Five Roles of the President

Chief Diplomat: This role confers power to the president to make treaties, acknowledge foreign governments and effect executive agreements.
Chief Legislator: The president influences lawmaking by creating congressional agenda, and uses persuasive strategies to ratify legislation.
Even though all the roles are essential, the chief legislator role is the most crucial for President Obama because the American laws will also influence foreign relations of the country and also influences all the other roles of the president.
Isolationism, Containment and Preemption
The concepts of isolationism, containment and preemption are all political and related to international relations and influence the relationship between one state and another. They all form part of foreign policy. Isolationism aims to pursue the interests of the United States treating the interests of other nations less important. For example, isolationism was a mechanism that kept the U.S. outside the Cold War up to when it realized that its interests were threatened. Containment focuses on restraining undesirable consequences to the U.S from spreading to other parts of the world or encroaching into the country itself. For example, the U.S used containment strategy to thwart the move of Soviet Union to spread communism to other parts of the world. On the other hand, the concept of preemption is often focused on thwarting a perceived incursion or gaining strategic advantage in a looming war. Preemptive war usually breaks the peace.